1. Filed of the Invention
The present invention relates to a vacuum pump including a housing having a suction opening in its high-vacuum region, a gas outlet opening in its high pressure region, and an intermediate chamber adjoining the gas outlet opening, pump-active cooperating rotor and stator components arranged in the housing for pumping gases from the suction opening to the outlet opening, with an end of the pump-active components adjoining the high pressure region being connected with the gas outlet opening via the intermediate chamber.
2. Description of the Prior Art
Vacuum pumps of the type described above can be formed, e.g., as turbomolecular pumps, or as molecular pumps, such as Holweck pumps, or as a combination of both types of pumps. The present invention also extends to combination of pumps that discharge against atmospheric pressure after realizing high pressure such as, e.g. regenerative pumps.
Such vacuum pumps are formed, as a rule, of a number of stages having different configurations, with each stage including rotor and stator components. The delivered gas flows through these pump-active components. The field of application of these pumps extends to processes in which a large quantity of easily condensable gases is formed, e.g., such as chemical processes or processes associated with manufacturing of semiconductors. With these pumps, gases flow from a high-vacuum region to a pressure region, in which a laminar flow prevails or in which the gas is compressed to atmospheric pressure. This means that in this region of high pressures, a relatively large quantity of gas is being pumped. In case when these gases are easily condensable, which is particularly the case at low temperatures, a significant amount of deposition of liquid or a solid materials takes place. This deposition leads to corrosion and etching that can result in destruction of separate components of a pump or an entire pump. This is particularly critical for types of pumps, which were discussed above, because their optimal operation can only be obtained at their high rotational speeds with a very small distance between the stationary and rotatable parts.
It was suggested to prevent formation of undesirable deposits by heating the critical regions (DE-A-197 02 456, EP-A 0646 290). In the constructions described in these references, the critical regions are heated by feeding heat via large-surfaces. The drawback of this solution consists in that the pump components, which are not subjected to precipitation, become heated, e.g., such as the housing high-vacuum connections, bearings, the drive. This leads, in addition to a very high energy consumption, to further drawbacks such as undesirable expansion of components having very narrow tolerances, damage of the drive bearing parts, and to a danger of injury to personnel as a result of a contact with a heated part.
Accordingly, the object of the preset invention is to provide a vacuum pump in which only the components susceptible to precipitation are heated.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, in the intermediate chamber, heating means connected with stator components located in the pressure region by a connection having a high thermal conductibility, and by providing thermal resistance means for separating the heating means from the housing.
The present invention ensures that only the critical components, i.e., only those components, which are particularly susceptible to precipitation of condensable material, are heated. By providing thermal connections having a high thermal conductibility, the heat is specifically directed to critical points. Other components, e.g. the housing, high-vacuum connections, bearings, and the drive, are protected from heating by thermal insulation. The advantages of these measures consists in reduced energy consumption, prevention of an undesirable expansion of components with narrow tolerances, prevention of injury to the personnel as a result of contact with heated parts. By increasing the flow rate, the pump output can be increased. The small heat capacity of the heated parts and of the stator components in the region of high pressure results in a reduced time of heating and, thereby, in reduced power consumption.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.